1. Technical Field
The present disclosure refers to a control apparatus for a load supply device.
2. Description of the Related Art
Control apparatuses are currently known for motors of the digital type, such as the one illustrated in FIG. 1. FIG. 1 shows a memory 1 where waveform samples WD are stored for driving a load 2, for example a load formed by the series of a resistance and an inductance. The samples WD are multiplied in amplitude by means of a digital multiplier 3, and the resulting modulated digital signals SD are inputs to a PWM digital converter 4 capable of providing pulse-width modulation signals for driving the switching device 5; the latter is connected between a supply voltage Vdd and ground GND and is responsible for supplying the motor 2.
In such control devices, the case where the average value of the signal at the output from the switching device 5 reflects the average value of the signal at the output of the PWM converter 3 occurs only when the supply voltage Vdd is kept constant.
However, in the majority of cases there are considerable variations in the supply voltage Vdd. To compensate for supply voltage variations, a circuit 6 is used that provides for the generation of a signal Scomp which results from the multiplication of the signal SD by a digital signal Vdig derived from the digital conversion of the supply voltage Vdd. In particular the circuit 6 includes an analog-digital converter 60 that converts the voltage Vdd into a digital signal Vdig, a circuit block 61 capable of inverting the signal Vdig and of multiplying it by a constant K, and another block 62 capable of multiplying the digital signal K/Vdig by the signal SD, thus obtaining the digital signal Scomp for feeding into the circuit block 3.
The block 61 can be structured as a look-up table (LUT) that contains a map of digital values K/Vdig or a suitable circuit that carries out the inversion in real time of the digital signal K/Vdig. The two solutions for making the block 61 are costly in terms of the digital resources required, given that a large occupation of silicon area is necessary in the integrated circuits.